code: Fix file listing omits first file in root.
#165 Showing count of the entities of the menu
issue,posting: Add Notification for comment.

* A user can watch by clicking watch button on issue or posting.
* The author, assignee and commenters become watcher automatically.
* Watchers receive a notification email when someone leaves a comment
  on the posting.
* Watchers can stop watching by toggling watch button.